153. In a repeater machine with 0 as an exponent, the base machine is applied 0 times. (a) What do these machines do to a piece of chalk? (b) What do you think the value of 60 is? You have seen that a hookup of repeater machines with the same base can be replaced by a single repeater machine. Similarly, when you multiply exponential expressions with the same base, you can replace them with a single expression.